1. Field of the Invention
The present invention relates to a radar apparatus for electrically carrying out scanning and, more particularly, to a radar apparatus suited for on-vehicle use.
2. Related Background Art
The on-vehicle radar apparatus is often utilized for recognition of cars etc. running ahead of a car and in that case, it is necessary to discriminate a preceding car from objects that cannot be obstacles because of their high altitudes from the road surface, such as road signs, information boards, and so on.
The invention to meet this demand is the on-vehicle monopulse radar apparatus for detecting a target by mechanically carrying out horizontal scanning and detecting an altitudinal bearing of the target by the monopulse method, as disclosed in Japanese Laid-open Patent Application No. 9-288178.
Since this on-vehicle monopulse radar apparatus can detect the altitudinal bearing of the target by the monopulse method, it can discriminate the cars from the road signs, information boards, etc. whose distances from the road surface are greater than those of the cars.
In this prior art, however, a plurality of receiving antennas of the mechanical scanning type are arrayed vertically, so that there are limitations on narrowing the space between the vertical receiving antennas. On the other hand, the monopulse method has a feature that the angular detection range becomes narrower as the antenna space increases. Therefore, the prior art described above had the problem that the angular range of detection in elevation was not assured sufficiently.